A nano-modified magnetic grease for TBM and its preparation method

Abstract

The present invention relates to the technical field of grease preparation, specifically disclosing a nano-modified magnetic grease for TBMs and a preparation method thereof. The nano-modified magnetic grease comprises the following raw materials in parts by weight: 5 to 15 parts of modified nano-magnetic particles, 60 to 80 parts of base oil, 1.5 to 4 parts of a surfactant, and 8 to 20 parts of a thickener; the thickener is a bio-based thickener modified with montmorillonite. The nano-modified magnetic grease provided by the present invention has high compatibility among its components, is a high-performance grease with excellent stability and minimal susceptibility to external moisture erosion. When applied to shield bearing seals, it can effectively lubricate and extend the bearing's service life.

Description

Technical Field

[0001] The invention relates to the technical field of grease preparation, and particularly discloses a nano-modified magnetic grease for TBM and a preparation method thereof. Background Art

[0002] A shield machine, also known as a tunnel boring machine, is a specialized engineering machine for tunnel excavation. It has functions such as excavating and cutting soil, transporting soil debris, assembling tunnel linings, and performing measurement and guidance correction. It is widely used in tunnel projects such as subways, railways, highways, municipal engineering, and hydropower projects. In recent years, my country has seen the rapid development of shield machines and the continuous advancement of shield technology. As one of the core components of shield machine equipment, the shield machine main bearing is the most commonly used component in mechanical reduction equipment. It supports the shield machine's propulsion of the cutterhead and excavates the soil through rotation. Its usage is very large. During shield construction, if the shield bearing seal grease is not tightly sealed and lubricated, it will cause damage to the bearing and its friction pair. Once damaged, it is extremely difficult to replace, causing huge losses to the shield construction and affecting the overall construction progress.

[0003] The lubrication system of a bearing generally includes lubricating oil and grease. Lubricating oil can protect bearings from rust and corrosion, but lubricating oil is highly fluid and easily evaporates. Grease, on the other hand, is a paste-like lubricating material composed of base oil, thickener, additives, and fillers. It has low fluidity and is less prone to leakage. It can simplify the bearing's peripheral structure and form a lubricating film on the bearing's friction surface, reducing friction and wear while also protecting the bearing from corrosion and oxidation. The main cause of bearing damage is a lack of lubrication, especially in bearings operating in open-air environments or in machinery in contact with water. Grease can quickly deteriorate and drain under the influence of water, resulting in a lack of bearing lubrication and damage.

[0004] The invention patent with application number 202311815056.8 discloses a lithium-based grease composition and its application method, including fatty acid, lithium carbonate, metal hydroxide, base oil and additives. Fatty acid, lithium carbonate and metal hydroxide are used as raw materials, and a lithium-based thickener is prepared through a certain process. A certain proportion of base oil and additives are added, and a new lithium-based grease composition is obtained after uniform dispersion in a disperser. This grease product not only has excellent high-temperature performance, mechanical stability, extreme pressure and anti-wear properties, and storage stability, but also has a low cost. It can replace existing lithium-based greases and meet the industry's universal requirements. However, the lithium-based grease composition has a large number of additives and still has the disadvantage of high grease consumption. It is not resistant to hydrolysis and is easily deteriorated and lost when washed by outdoor water, resulting in the lack of bearing lubrication and causing damage.

[0005] In view of this, it is particularly important that the present application discloses a nano-modified magnetic grease for TBM and a preparation method thereof. Summary of the Invention

[0006] To address the shortcomings of the prior art, the present invention aims to provide a nano-modified magnetic grease for TBMs and its preparation method. The nano-modified magnetic grease provided by the present invention exhibits high compatibility among its components, is a high-performance grease with excellent stability and minimal susceptibility to external moisture erosion. When applied to shield bearing seals, it effectively lubricates and extends bearing life.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0008] On one hand, the present invention provides a nano-modified magnetic grease for TBM, which comprises the following raw materials in parts by weight: 5 to 15 parts of modified nano-magnetic particles, 60 to 80 parts of base oil, 1.5 to 4 parts of surfactant and 8 to 20 parts of thickener; wherein the thickener is a montmorillonite-modified bio-based thickener.

[0009] In some embodiments of the present invention, the modified nanomagnetic particles are prepared by the following steps:

[0010] Preparation of S1-nanomagnetic particles: Fe3O4 nanoparticles and deionized water were added to a reactor, the pH was adjusted to 5-5.5, anhydrous ethanol and tetraethyl silicate were added in sequence, and the mixture was stirred for 1-2 hours. The pH was adjusted to 9-10, and the mixture was stirred for 1-2 hours. After separation, the mixture was washed and dried to a constant weight to obtain nanomagnetic particles.

[0011] Preparation of S2-modified nanomagnetic particles: Anhydrous ethanol, nanomagnetic particles and amino-group-containing silane modifier are added to the reactor in sequence, ultrasonically dispersed for 15 to 30 minutes, stirred, condensed and refluxed in an oil bath for 1 to 2 days, then washed, centrifuged and dried to constant weight to obtain modified nanomagnetic particles.

[0012] In some embodiments of the present invention, in step S1, the mass ratio of the Fe3O4 nanoparticles to tetraethyl silicate is (5-7):1.

[0013] Preferably, in step S1, the mass ratio of the Fe3O4 nanoparticles to tetraethyl silicate is 6:1.

[0014] In some embodiments of the present invention, in step S2, the amino group-containing silane modifier is 3-aminopropyltriethoxysilane.

[0015] In some embodiments of the present invention, in step S2, the mass ratio of the nanomagnetic particles to the amino group-containing silane modifier is 1:(1.2-2).

[0016] Preferably, in step S2, the mass ratio of the nanomagnetic particles to the amino group-containing silane modifier is 1:1.8.

[0017] Preferably, in step S1, the amount of deionized water added is 3 to 5 times the mass of the Fe3O4 nanoparticles.

[0018] Further preferably, in step S1, the amount of deionized water added is 4 times the mass of the Fe3O4 nanoparticles.

[0019] Preferably, in step S1, the amount of anhydrous ethanol added is 10 to 12 times the mass of tetraethyl silicate.

[0020] Further preferably, in step S1, the amount of anhydrous ethanol added is 11 times the mass of tetraethyl silicate.

[0021] Preferably, in step S2, the amount of anhydrous ethanol added is 80 to 100 times the total mass of the nanomagnetic particles and the amino group-containing silane modifier.

[0022] Further preferably, in step S2, the amount of anhydrous ethanol added is 90 times the total mass of the nanomagnetic particles and the amino group-containing silane modifier.

[0023] The applicant used tetraethyl silicate as a silicon source to compound with Fe3O4 nanoparticles to form silica-coated nanomagnetic particles. As a non-magnetic particle, silica is gradually expelled to the surface of Fe3O4 under the action of a non-uniform magnetic field and uniformly coats the outer layer of Fe3O4 to form a core-shell, which can delay the oxidation of Fe3O4 and protect it. The modified nanomagnetic particles exhibit superparamagnetism. Under the joint action of the magnetic field, the stability of the internal microstructure of the nanomagnetic particles is improved, and its creep recovery ability is also improved. The grease structure can be restored during shutdown, effectively reducing the risk of oil leakage. The applicant also conducted a study on the nanomagnetic particles. The surface of the magnetic particles is treated with amino treatment, which makes them more compatible when mixed with other raw materials of the grease system. The silicon-oxygen bonds and amino and other functional groups between the 3-aminopropyltriethoxysilane molecules form strong chemical bonds in the grease system. When the grease is washed by water, the ethoxy groups therein form hydrogen bonds with the water molecules, thereby improving the stability and reducing the adverse effects of water washing. At the same time, with the support of the viscosity of the system, the modified nano-magnetic particles are stable under pure gravity. When subjected to shear force, they become thinner, which is conducive to fully entering the friction gap, reducing the internal resistance of the grease, and facilitating the realization of the sealing advantages of the magnetic material.

[0024] Preferably, the base oil is a naphthenic base oil.

[0025] Preferably, the surfactant is oleic acid or a surfactant containing a sulfonic acid group.

[0026] Further preferably, the surfactant is a surfactant containing a sulfonic acid group.

[0027] Preferably, the surfactant is dodecylbenzenesulfonic acid.

[0028] The present invention adds a specially selected surfactant containing a sulfonic acid group, which not only plays a wetting and coating role but also helps absorb a certain amount of water, thereby preventing the grease from being lost and playing an auxiliary bearing sealing role.

[0029] In some embodiments of the present invention, the preparation steps of the montmorillonite-modified bio-based thickener are as follows:

[0030] (1) Preparation of organic modified montmorillonite: Montmorillonite and anhydrous ethanol were added to a reactor, stirred evenly, and then a silane coupling agent was added. The temperature was raised to 70-90°C, and the reaction was carried out for 1-3 hours. After washing and centrifugation, the sediment was dried to a constant weight to obtain the organic modified montmorillonite.

[0031] (2) Preparation of montmorillonite-modified bio-based thickener: Add micronized fiber cellulose and deionized water into a container, stir for 8 to 10 hours, ultrasonically disperse for 20 to 30 minutes, transfer to a reactor, add organic modified montmorillonite, homogenize at 8000 to 12000 r / min for 3 to 6 minutes, ultrasonically treat for 3 to 6 minutes, and stir for 1 to 3 hours to obtain the montmorillonite-modified bio-based thickener.

[0032] Preferably, the preparation steps of the montmorillonite-modified bio-based thickener are as follows:

[0033] (1) Preparation of organically modified montmorillonite: Montmorillonite and anhydrous ethanol were added to a reactor, stirred evenly, and then a silane coupling agent was added. The temperature was raised to 80°C, and the reaction was carried out for 2 hours. After washing and centrifugation, the sediment was dried to a constant weight to obtain organically modified montmorillonite.

[0034] (2) Preparation of montmorillonite-modified bio-based thickener: Micronized fiber cellulose and deionized water were added to a container, stirred for 9 hours, ultrasonically dispersed for 25 minutes, transferred to a reactor, and then organic modified montmorillonite was added. The mixture was homogenized at 10,000 r / min for 4.5 minutes, ultrasonically treated for 4.5 minutes, and stirred for 2 hours to obtain the montmorillonite-modified bio-based thickener.

[0035] In some embodiments of the present invention, in step (1), the silane coupling agent is perfluorodecyltriethoxysilane.

[0036] In some embodiments of the present invention, in step (1), the mass ratio of the montmorillonite to the silane coupling agent is 1:(0.1-0.5).

[0037] Preferably, in step (1), the mass ratio of the montmorillonite to the silane coupling agent is 1:0.3.

[0038] In some embodiments of the present invention, in step (2), the mass ratio of the micronized fiber cellulose to the organically modified montmorillonite is 1:(1-1.3).

[0039] Preferably, in step (2), the mass ratio of the micronized fiber cellulose to the organically modified montmorillonite is 1:1.2.

[0040] Preferably, in step (1), the amount of anhydrous ethanol added is 20 to 30 times the total mass of montmorillonite and the silane coupling agent.

[0041] Further preferably, in step (1), the amount of anhydrous ethanol added is 25 times the total mass of montmorillonite and the silane coupling agent.

[0042] Preferably, in step (2), the amount of deionized water added is 500 to 1000 times the mass of the micronized fiber cellulose.

[0043] Further preferably, in step (2), the amount of deionized water added is 750 times the mass of the micronized fiber cellulose.

[0044] The applicant organically modified montmorillonite to reduce the influence of its natural hydrophilic and oleophobic properties on the grease system, and specifically selected the ratio of modified montmorillonite to micronized fiber cellulose to prepare a high-efficiency thickener that can effectively exert the thickening effect on the grease system at a relatively low addition amount. The possible reason is that when the thickener is added to the grease system, the modified montmorillonite forms a stable percolation structure in the grease system, and a specific amount of micronized fiber cellulose is organically integrated into the permeation structure and forms a strengthening effect, while forming an entangled network structure similar to lithium soap, but its small diameter can produce a greater degree of tortuosity than lithium soap. On the other hand, the modified montmorillonite and micronized fiber cellulose mixed in a specific ratio can synergize with the nanomagnetic particles in the grease system due to their small particles and low hardness, playing a role similar to that of micro ball bearings, thereby effectively reducing friction and wear; on the other hand, the organic modified montmorillonite, due to the introduction of large side chains, increases the distance between molecular chains, which can have a certain anti-aggregation effect on the modified nanomagnetic particles in the system, unexpectedly increasing the dispersibility of the modified nanomagnetic particles and thus achieving better stability and compatibility with other components.

[0045] On the other hand, the present invention also provides a method for preparing nano-modified magnetic grease for TBM, comprising the following steps: adding a surfactant and modified nano-magnetic particles to a reactor in sequence, stirring at 40-60°C for 15-30 minutes, then ultrasonically dispersing for 15-30 minutes, then transferring it to a reactor containing base oil, stirring at 50-60°C for 40-60 minutes, then ultrasonically dispersing for 30-60 minutes, heating to 50-80°C, adding a thickener, stirring for 15-30 minutes, cooling to room temperature, and then ultrasonically dispersing for 30-50 minutes to obtain the nano-modified magnetic grease.

[0046] Compared with the prior art, the present invention has the following beneficial effects:

[0047] (1) The nano-modified magnetic grease for TBM prepared by the present invention is prepared by preparing a modified nano-magnetic particle and a montmorillonite-modified bio-based thickener, preferably using a base oil as a base carrier liquid, adding a surfactant, and obtaining a high-performance grease with good stability and little influence from external water erosion through the preferred preparation steps. When applied to shield bearing seals, it can effectively exert lubrication effect and increase the service life of the bearings;

[0048] (2) The present invention uses tetraethyl silicate as a silicon source to form silica-coated nanomagnetic particles in combination with Fe3O4 nanoparticles. The stability of the internal microstructure of the modified nanomagnetic particles is improved, and the creep recovery ability thereof is also improved simultaneously. The grease structure can be restored during shutdown, effectively reducing the risk of oil leakage. The present invention also performs surface amino treatment on the nanomagnetic particles, which enables better compatibility when mixed with other raw materials of the grease system, so that the grease remains stable when subjected to water scouring, thereby reducing the adverse effects of water scouring. At the same time, under the support of the viscosity of the system, the modified nanomagnetic particles become thinner when subjected to shear force, which is conducive to fully entering the friction gap, reducing the internal resistance of the grease, and facilitating the utilization of the sealing advantages of the magnetic material.

[0049] (3) The present invention reduces the influence of its natural hydrophilic and oleophobic properties on the grease system by organically modifying montmorillonite, and obtains a high-efficiency thickener at a specific ratio of modified montmorillonite and micronized fiber cellulose, which can achieve a more efficient thickening effect than the commonly used lithium soap thickener at a lower addition amount; on the other hand, the modified montmorillonite and micronized fiber cellulose mixed in a specific ratio can also synergize with the nanomagnetic particles in the grease system, playing a role similar to that of micro ball bearings, thereby effectively reducing friction and wear; on another hand, the organic modified montmorillonite, due to the introduction of large-volume side chains, increases the distance between molecular chains, which can produce a certain anti-aggregation effect on the modified nanomagnetic particles in the system, unexpectedly increasing the dispersibility of the modified nanomagnetic particles, and thus better stable compatibility with other components. DETAILED DESCRIPTION

[0050] The present invention will be described below in conjunction with specific embodiments. It should be noted that the following examples are illustrative of the present invention and are intended only to illustrate the present invention and are not intended to limit the present invention. Other combinations and various modifications within the scope of the present invention may be made without departing from the spirit or scope of the present invention.

[0051] Unless otherwise specified, the following reagents can be easily obtained from commercial companies. Among them, Fe3O4 nanoparticles were purchased from Zhejiang Yamei Nano Technology Co., Ltd.; micronized fiber cellulose was purchased from Wuhan Kemik Biomedical Technology Co., Ltd.; and cyclohexane base oil was purchased from Xingtai Quande Chemical Co., Ltd.

[0052] Preparation Example 1

[0053] The preparation steps of modified nanomagnetic particles I are as follows:

[0054] Preparation of S1-nanomagnetic particles: Add 6g of Fe3O4 nanoparticles and 24mL of deionized water to a reactor, adjust the pH to 5, add 11mL of anhydrous ethanol and 1g of tetraethyl silicate in sequence, stir for 1.5h, adjust the pH to 9.5, continue stirring for 1.5h, separate, wash once with anhydrous ethanol and four times with deionized water, and dry at 55°C to constant weight to obtain nanomagnetic particles;

[0055] Preparation of S2-modified nanomagnetic particles: 504 mL of anhydrous ethanol, 2 g of nanomagnetic particles and 3.6 g of 3-aminopropyltriethoxysilane were added to the reactor in sequence, and ultrasonically dispersed for 23 minutes. The mixture was stirred, condensed and refluxed in an oil bath at 90°C for 1.5 days, and then washed with anhydrous ethanol and centrifuged twice. The mixture was dried at 55°C to constant weight to obtain modified nanomagnetic particles I.

[0056] Preparation Example 2

[0057] The preparation steps of modified nanomagnetic particles II are the same as those of Preparation Example 1, except that 4 g of Fe3O4 nanoparticles are added in step S1.

[0058] Preparation Example 3

[0059] The preparation steps of modified nanomagnetic particles III are the same as those of Preparation Example 1, except that in step S1, 7 g of Fe3O4 nanoparticles are added.

[0060] Preparation Example 4

[0061] The preparation steps of the modified nanomagnetic particles IV are the same as those of Preparation Example 1, except that in step S2, 2.2 g of 3-aminopropyltriethoxysilane is added.

[0062] Preparation Example 5

[0063] The preparation steps of the modified nanomagnetic particles V are the same as those of Preparation Example 1, except that in step S2, 4.2 g of 3-aminopropyltriethoxysilane is added.

[0064] Preparation Example 6

[0065] The preparation steps of the first montmorillonite-modified bio-based thickener are as follows:

[0066] (1) Preparation of organically modified montmorillonite: 5 g of montmorillonite and 163 mL of anhydrous ethanol were added to a reactor and stirred evenly. 1.5 g of perfluorodecyltriethoxysilane was then added and the mixture was heated to 80°C for 2 h. The mixture was washed with anhydrous ethanol and centrifuged twice. The sediment was dried at 60°C to a constant weight to obtain organically modified montmorillonite.

[0067] (2) Preparation of montmorillonite-modified bio-based thickener: 2 g of micronized fiber cellulose and 1500 mL of deionized water were added to a container, stirred for 9 h, ultrasonically dispersed for 25 min, transferred to a reactor, and then 2.4 g of organic modified montmorillonite was added. The mixture was homogenized at 10,000 r / min for 4.5 min, ultrasonically treated for 4.5 min, and stirred for 2 h to obtain the first montmorillonite-modified bio-based thickener.

[0068] Preparation Example 7

[0069] The preparation steps of the second montmorillonite-modified bio-based thickener are the same as those of Preparation Example 6, except that 0.25 g of perfluorodecyltriethoxysilane is added in step (1).

[0070] Preparation Example 8

[0071] The preparation steps of the third montmorillonite-modified bio-based thickener are the same as those in Preparation Example 6, except that 3 g of perfluorodecyltriethoxysilane is added in step (1).

[0072] Preparation Example 9

[0073] The preparation steps of the fourth montmorillonite-modified bio-based thickener are the same as those of Preparation Example 6, except that 1 g of organically modified montmorillonite is added in step (2).

[0074] Preparation Example 10

[0075] The preparation steps of the fifth montmorillonite-modified bio-based thickener are the same as those of Preparation Example 6, except that 2.8 g of organically modified montmorillonite is added in step (2).

[0076] Preparation Example 11

[0077] The preparation steps of nanomagnetic particles are as follows:

[0078] Add 6 g of Fe3O4 nanoparticles and 24 mL of deionized water to the reactor, adjust the pH to 5, add 11 mL of anhydrous ethanol and 1 g of tetraethyl silicate in sequence, stir for 1.5 h, adjust the pH to 9.5, continue stirring for 1.5 h, separate, wash once with anhydrous ethanol, wash 4 times with deionized water, and dry at 55 ° C to constant weight to obtain nanomagnetic particles.

[0079] Unless otherwise specified, in the following examples and comparative examples, the base oils used are all cycloparaffinic base oils, and the surfactants used are all dodecylbenzenesulfonic acid.

[0080] Example 1

[0081] A nano-modified magnetic grease for TBM, comprising the following raw materials in parts by weight: 10 parts of modified nano-magnetic particles I, 70 parts of base oil, 2.75 parts of surfactant, and 14 parts of a first montmorillonite-modified bio-based thickener;

[0082] The preparation method of the nano-modified magnetic grease for TBM in this embodiment comprises the following steps: adding a surfactant and modified nano-magnetic particles I to a reactor in sequence, stirring at 50°C for 23 minutes, then ultrasonically dispersing for 23 minutes, transferring the mixture to a reactor containing base oil, stirring at 55°C for 50 minutes, then ultrasonically dispersing for 45 minutes, heating to 65°C, adding a first montmorillonite-modified bio-based thickener, stirring for 23 minutes, cooling to room temperature, and then ultrasonically dispersing for 40 minutes to obtain the nano-modified magnetic grease.

[0083] Example 2

[0084] A nano-modified magnetic grease for TBM, comprising the following raw materials in parts by weight: 5 parts of modified nano-magnetic particles I, 60 parts of base oil, 1.5 parts of surfactant, and 8 parts of a first montmorillonite-modified bio-based thickener;

[0085] The preparation method of the nano-modified magnetic grease for TBM in this embodiment comprises the following steps: adding a surfactant and modified nano-magnetic particles I to a reactor in sequence, stirring at 40°C for 30 minutes, then ultrasonically dispersing for 30 minutes, transferring the mixture to a reactor containing base oil, stirring at 50°C for 60 minutes, then ultrasonically dispersing for 60 minutes, heating to 50°C, adding a first montmorillonite-modified bio-based thickener, stirring for 30 minutes, cooling to room temperature, and then ultrasonically dispersing for 30 minutes to obtain the nano-modified magnetic grease.

[0086] Example 3

[0087] A nano-modified magnetic grease for TBM, comprising the following raw materials in parts by weight: 15 parts of modified nano-magnetic particles I, 80 parts of base oil, 4 parts of surfactant, and 20 parts of a first montmorillonite-modified bio-based thickener;

[0088] The preparation method of the nano-modified magnetic grease for TBM in this embodiment comprises the following steps: adding a surfactant and modified nano-magnetic particles I to a reactor in sequence, stirring at 60°C for 15 minutes, ultrasonically dispersing for 15 minutes, transferring the mixture to a reactor containing base oil, stirring at 60°C for 40 minutes, ultrasonically dispersing for 30 minutes, heating to 80°C, adding a first montmorillonite-modified bio-based thickener, stirring for 15 minutes, cooling to room temperature, and ultrasonically dispersing for 40 minutes to obtain the nano-modified magnetic grease.

[0089] Example 4

[0090] A nano-modified magnetic grease for TBM and a preparation method thereof. The specific implementation method is the same as that of Example 1, except that the modified nano-magnetic particles II are used to replace the modified nano-magnetic particles I in equal amounts.

[0091] Example 5

[0092] A nano-modified magnetic grease for TBM and a preparation method thereof. The specific implementation method is the same as that of Example 1, except that the modified nano-magnetic particles III are used to replace the modified nano-magnetic particles I in equal amounts.

[0093] Example 6

[0094] A nano-modified magnetic grease for TBM and a preparation method thereof. The specific implementation method is the same as that of Example 1, except that the modified nano-magnetic particles IV are used to replace the modified nano-magnetic particles I in equal amounts.

[0095] Example 7

[0096] A nano-modified magnetic grease for TBM and a preparation method thereof. The specific implementation method is the same as that of Example 1, except that the modified nano-magnetic particles V are used to replace the modified nano-magnetic particles I in equal amounts.

[0097] Example 8

[0098] A nano-modified magnetic grease for TBM and a preparation method thereof. The specific implementation method is the same as that of Example 1, except that the first montmorillonite-modified bio-based thickener is replaced by an equal amount of a second montmorillonite-modified bio-based thickener.

[0099] Example 9

[0100] A nano-modified magnetic grease for TBM and a preparation method thereof. The specific implementation method is the same as that of Example 1, except that the first montmorillonite-modified bio-based thickener is replaced by an equal amount of a third montmorillonite-modified bio-based thickener.

[0101] Example 10

[0102] A nano-modified magnetic grease for TBM and a preparation method thereof. The specific implementation method is the same as that of Example 1, except that the first montmorillonite-modified bio-based thickener is replaced by an equal amount of a fourth montmorillonite-modified bio-based thickener.

[0103] Example 11

[0104] A nano-modified magnetic grease for TBM and a preparation method thereof. The specific implementation method is the same as that of Example 1, except that the first montmorillonite-modified bio-based thickener is replaced by an equal amount of a fifth montmorillonite-modified bio-based thickener.

[0105] Comparative Example 1

[0106] A nano-modified magnetic grease for TBM and a preparation method thereof. The specific implementation method is the same as that of Example 1, except that the modified nano-magnetic particles I are replaced by an equal amount of nano-magnetic particles.

[0107] Comparative Example 2

[0108] A nano-modified magnetic grease for TBM and a preparation method thereof, wherein the specific implementation manner is the same as that of Example 1, except that an equal amount of micronized fiber cellulose is used to replace the first montmorillonite-modified bio-based thickener.

[0109] Performance Testing

[0110] The nano-modified magnetic greases obtained in Examples 1-11 and Comparative Examples 1-2 were subjected to the following performance tests. The specific test results are shown in Table 1:

[0111] (1) Stability performance test: The nano-modified magnetic grease obtained in Examples 1-11 and Comparative Examples 1-2 was subjected to a Zeta potential test. An absolute value of the Zeta potential greater than 30 mV indicated no agglomeration and good stability.

[0112] (2) Water shock resistance test: The nano-modified magnetic grease obtained in Examples 1-11 and Comparative Examples 1-2 was placed in water and continuously flushed with water at 5 mL / s±0.5 mL / s for 5 min. The grease was transferred to an oven and dried at 80°C for 1 h. The mass loss of the nano-modified magnetic grease was measured and the loss percentage was calculated. The smaller the loss percentage, the better the water shock resistance.

[0113] Table 1

[0114]

[0115]

[0116] As shown in Table 1, the nano-modified magnetic grease for TBM provided in Examples 1 to 3 of the present invention is a high-performance grease with good stability and little effect from external water erosion;

[0117] In Examples 4 and 5, the mass ratio of Fe3O4 nanoparticles to tetraethyl silicate was changed, which affected the coating effect of silica on Fe3O4 nanoparticles, thereby affecting the magnetic distribution of the nanomagnetic particles and reducing their stability.

[0118] In Examples 6 and 7, the mass ratio of nanomagnetic particles to 3-aminopropyltriethoxysilane was changed. The entanglement of the molecular chains caused the nanomagnetic particles to agglomerate, which limited the compatibility and led to a decrease in water shock resistance.

[0119] In Examples 8 and 9, the mass ratio of montmorillonite to perfluorodecyltriethoxysilane was changed, which affected the organic modification effect of the montmorillonite, especially causing a decrease in stability and water shock resistance.

[0120] In Examples 10 and 11, the mass ratio of micronized cellulose fiber and organically modified montmorillonite was changed. Due to the decrease in the proportion of effective percolation structure, the strengthening effect was affected, resulting in a decrease in the performance of the prepared thickener. At the same time, the system was poorly dispersed, the particles agglomerated, and the effectiveness of each component decreased, ultimately affecting the stability and water shock resistance of the nano-modified magnetic grease.

[0121] Comparison of Comparative Example 1 with Example 1 shows that when the modified nano-magnetic particles I are replaced by the same amount of nano-magnetic particles, the stability and water shock resistance of the nano-modified magnetic grease are reduced;

[0122] Comparison of Comparative Example 2 with Example 1 shows that when the first montmorillonite-modified bio-based thickener is replaced by an equal amount of micronized fiber cellulose, the thickening effect of the system is reduced, and the compatibility and stability within the system are affected, resulting in varying degrees of reduction in the stability and water shock resistance of the nano-modified magnetic grease.

[0123] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as a preferred embodiment, it is not intended to limit the present invention. Any technician familiar with the present profession can make some changes or modifications to equivalent embodiments of equivalent changes using the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A nano-modified magnetic grease for TBM, characterized in that: The nano-modified magnetic grease comprises the following raw materials in parts by weight: 5 to 15 parts of modified nano-magnetic particles, 60 to 80 parts of base oil, 1.5 to 4 parts of surfactant, and 8 to 20 parts of thickener; wherein the thickener is a montmorillonite-modified bio-based thickener; The preparation steps of the modified nanomagnetic particles are as follows: Preparation of S1-nanomagnetic particles: Fe3O4 nanoparticles and deionized water were added to a reactor, the pH was adjusted to 5-5.5, anhydrous ethanol and tetraethyl silicate were added in sequence, and the mixture was stirred for 1-2 hours. The pH was adjusted to 9-10, and the mixture was stirred for 1-2 hours. After separation, the mixture was washed and dried to a constant weight to obtain nanomagnetic particles. Preparation of S2-modified nanomagnetic particles: Anhydrous ethanol, nanomagnetic particles, and an amino-containing silane modifier are sequentially added to a reactor, dispersed by ultrasound for 15 to 30 minutes, stirred, condensed, and refluxed in an oil bath for 1 to 2 days, and then washed, centrifuged, and dried to a constant weight to obtain modified nanomagnetic particles; In step S2, the mass ratio of the nanomagnetic particles to the amino group-containing silane modifier is 1:(1.2-2); The preparation steps of the montmorillonite-modified bio-based thickener are as follows: (1) Preparation of organic modified montmorillonite: Montmorillonite and anhydrous ethanol were added to a reactor, stirred evenly, and then a silane coupling agent was added. The temperature was raised to 70-90°C, and the reaction was carried out for 1-3 hours. After washing and centrifugation, the sediment was dried to a constant weight to obtain the organic modified montmorillonite. (2) Preparation of montmorillonite-modified bio-based thickener: Add micronized fiber cellulose and deionized water into a container, stir for 8 to 10 hours, ultrasonically disperse for 20 to 30 minutes, transfer to a reactor, add organic modified montmorillonite, homogenize at 8000 to 12000 r / min for 3 to 6 minutes, ultrasonically treat for 3 to 6 minutes, and stir for 1 to 3 hours to obtain the montmorillonite-modified bio-based thickener; In step (1), the mass ratio of the montmorillonite to the silane coupling agent is 1:(0.1-0.5); In step (2), the mass ratio of the micronized fiber cellulose to the organic modified montmorillonite is 1:(1-1.3).

2. The nano-modified magnetic grease for TBM according to claim 1, characterized in that: In step S1, the mass ratio of the Fe3O4 nanoparticles to tetraethyl silicate is (5-7):

1.

3. The nano-modified magnetic grease for TBM according to claim 1, characterized in that: In step S2, the amino group-containing silane modifier is 3-aminopropyltriethoxysilane.

4. The nano-modified magnetic grease for TBM according to claim 1, characterized in that: In step (1), the silane coupling agent is perfluorodecyltriethoxysilane.

5. A method for preparing the nano-modified magnetic grease for TBM according to any one of claims 1 to 4, characterized in that: The method comprises the following steps: sequentially adding a surfactant and modified nano magnetic particles into a reactor, stirring at 40-60°C for 15-30 minutes, ultrasonically dispersing for 15-30 minutes, transferring the particles into a reactor containing base oil, stirring at 50-60°C for 40-60 minutes, ultrasonically dispersing for 30-60 minutes, heating to 50-80°C, adding a thickener, stirring for 15-30 minutes, cooling to room temperature, and ultrasonically dispersing for 30-50 minutes to obtain the nano modified magnetic grease.

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